Whenever you see the 3rd tone described in a textbook it will always be shown as a falling-rising tone. Unfortunately it is hardly ever pronounced this way. A much better conception of the third tone is a “low tone” but even that isn’t sufficient.
The complexity arises because the third tone is almost always altered by the tones used around it. As a result it causes the most difficulty for people learning Chinese.
This is the best way I’ve found to help people learn the 3rd tone fast by being able to compare their pitch graph with that of their native speaking teacher.
The other thing you need to practice are the third tone tone-change. When a 3rd tone is followed by a second 3rd tone the first 3rd tone becomes a 2nd tone. Try saying that ten times fast! Here’s an example that is much easier.
你好 nǐhǎo is actually pronounced ní hǎo.
I’ve written more detailed articles on the 3rd tone (and tones in general) here:
Because of tone change rules you should always practice Chinese pronunciation and tones in the context of WORDS not isolated character sounds. That’s the next topic I want to look at in this series.